5.4 Data marshalling support

These routines allow C code to work with serialized objects using the
same data format as the marshal module. There are functions
to write data into the serialization format, and additional functions
that can be used to read the data back. Files used to store marshalled
data must be opened in binary mode.

Numeric values are stored with the least significant byte first.

The module supports two versions of the data format: version 0 is the
historical version, version 1 (new in Python 2.4) shares interned
strings in the file, and upon unmarshalling. Py_MARSHAL_VERSION
indicates the current file format (currently 1).

void PyMarshal_WriteLongToFile(

long value, FILE *file, int version)

Marshal a long integer, value, to file. This
will only write the least-significant 32 bits of value;
regardless of the size of the native long type.

Changed in version 2.4:
version indicates the file format.

void PyMarshal_WriteObjectToFile(

PyObject *value,
FILE *file, int version)

Marshal a Python object, value, to file.

Changed in version 2.4:
version indicates the file format.

PyObject* PyMarshal_WriteObjectToString(

PyObject *value, int version)

Return value:New reference.

Return a string object containing the marshalled representation of
value.

Changed in version 2.4:
version indicates the file format.

The following functions allow marshalled values to be read back in.

XXX What about error detection? It appears that reading past the end
of the file will always result in a negative numeric value (where
that's relevant), but it's not clear that negative values won't be
handled properly when there's no error. What's the right way to tell?
Should only non-negative values be written using these routines?

long PyMarshal_ReadLongFromFile(

FILE *file)

Return a C long from the data stream in a FILE*
opened for reading. Only a 32-bit value can be read in using
this function, regardless of the native size of long.

int PyMarshal_ReadShortFromFile(

FILE *file)

Return a C short from the data stream in a FILE*
opened for reading. Only a 16-bit value can be read in using
this function, regardless of the native size of short.

PyObject* PyMarshal_ReadObjectFromFile(

FILE *file)

Return value:New reference.

Return a Python object from the data stream in a FILE*
opened for reading. On error, sets the appropriate exception
(EOFError or TypeError) and returns NULL.

PyObject* PyMarshal_ReadLastObjectFromFile(

FILE *file)

Return value:New reference.

Return a Python object from the data stream in a FILE*
opened for reading. Unlike
PyMarshal_ReadObjectFromFile(), this function assumes
that no further objects will be read from the file, allowing it to
aggressively load file data into memory so that the de-serialization
can operate from data in memory rather than reading a byte at a time
from the file. Only use these variant if you are certain that you
won't be reading anything else from the file. On error, sets the
appropriate exception (EOFError or
TypeError) and returns NULL.

PyObject* PyMarshal_ReadObjectFromString(

char *string,
Py_ssize_t len)

Return value:New reference.

Return a Python object from the data stream in a character buffer
containing len bytes pointed to by string. On error,
sets the appropriate exception (EOFError or
TypeError) and returns NULL.